package ListNode;



import java.util.*;
 class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}
public class PalindromeList{
    public boolean chkPalindrome(ListNode A) {
        // write code here  
         if(A==null){
          return true;
        }
         // write code here
        //找到中点
        ListNode fast=A;
        ListNode slow=fast;
        ListNode cur=fast;
        while(fast!=null&&fast.next!=null){
            fast=fast.next.next;
            slow=slow.next;
        }
        //翻转
        cur=slow.next;
        while(cur!=null){
            ListNode curNext=cur.next;
            cur.next=slow;
            slow=cur;
            cur=curNext;
        }
        while(A!=slow){
            if(A.val!=slow.val){
                return false;
            }
            if(A.next!=slow){
                return true;
            }
            A=A.next;
            slow=slow.next;
        }
        return true;
    
    }
}

	

